1. Field of the Invention
This invention relates to a continuous mining machine, and more particularly, to a continuous mining machine having a cutter drum member with extendable end portions. The present invention is directed to a means for locking the cutter drum extensions in their extended position.
2. Description of the Prior Art
In a continuous-mining apparatus of the type employed in this invention, a cutting head mechanism is used to dislodge material from a mine vein and is operable to provide mine passageway or room into which the apparatus advances and mining progresses. The cutting head mechanism is pivotably mounted on a mobile base to swing in a vertical plane between the mine roof and floor and includes a rotary drum cutting head assembly arranged on a horizontal transverse axis and having teeth or bits which tear away and dislodge the mineral. The apparatus also includes a conventional loading head for gathering the loose mineral on the mine floor and moving it rearwardly and inwardly towards the forward receiving portions of the conveying means of the apparatus. The rotary drum cutting assembly has end portions thereof which can be selectively extended or retracted, to respectively, dislodge mineral from the ribs and corners of the mine passageway and reduce the effective length of the cutting head assembly to provide clearance at the sides of the assembly.
A good example of a mining machine drum cutter extension means in which the present invention can be utilized is shown in U.S. Pat. No. 3,617,093 issued to E. A. Bailey on Nov. 2, 1971. A second patent, U.S. Pat. No. 3,695,725 issued to E. F. Pendalino on Oct. 3, 1972 discloses a similar structure. These two patents are assigned to the assignee of the present application. The teachings of these two U.S. patents are incorporated in this application by reference.
U.S. Pat. No. 3,516,712 discloses a mining machine with an extendable head having a spring return mechanism. The means for extending the extensible head is a hydraulic cylinder.
U.S. Pat. Nos. 3,844,618 and 3,874,735 disclose mining machines having rotary motor extended cutting heads. In these patents a rotary motor drives a screw system which extends the cutting head.
It has been found that after the cutting head has been extended forces developed during mining tend to move the cutting head towards its retracted position by driving hydraulic fluid back across the valve shown in FIG. 5 of U.S. Pat. No. 3,617,093 or backing off the screw threads disclosed in U.S. Pat. Nos. 3,844,618 and 3,874,735.
In addition, dust and grid from the mining operation gets into the hydraulic system degrading the operation of hydraulic pumps, control valves, seals and check valves and thereby permitting fluid leakage around various components in the hydraulic system. Degradation of the seals causes leakage of fluid out of the system. The net effect of this degradation is to permit nonselective retraction of the end extension portions during operation of the mining machine.
Consequently, the present invention relates to an automatic means for locking the cutter head extensions in these extended positions utilizing one or more mechanical latchs. As will be described below the locking means of the present invention maintains the cutter drum in its extended position and unlatches the same for movement towards its retracted position without the addition of any control features on the mining machine.